A number of investigations have been carried out with respect to using various kinds of fading inhibitors in photographic systems for the color diffusion process with the intention of improving upon the light resistance of color images. For instance, Research Disclosure, Volume 151, Number 15162, from the lower part of the left column in page 81 to the upper part of the left column in page 82 (Nov. 1976) discloses the addition of various kinds of fading inhibitors to mordanting layers of photographic systems for the color diffusion process.
A large number of studies of mordants for fixing dyes in photographic materials for color diffusion transfer process have been undertaken. Specific examples of such mordants include vinylpyridine polymers and vinylpyridinium polymers disclosed in U.S. Pat. Nos. 2,548,564, 3,148,061, 3,756,814 and so on; water-soluble quaternary ammonium salt polymers disclosed in U.S. Pat. No. 3,709,690 and so on; water-insoluble mordants described in U.S. Pat. No. 3,898,088; water-dispersable latex mordants disclosed in U.S. Pat. No. 3,958,995 and so on; reactive mordants capable of being covalently bound to dyes disclosed in U.S. Pat. No. 4,168,976 and so on. Among these mordants, water-dispersable latex mordants which are difficult to move from the mordanting layers to other layers and which enable aqueous coating of the mordanting layers are especially suitable for the above-described purpose. Water-dispersable latex mordants are disclosed in Japanese Patent Application (OPI) Nos. 115228/79, 145529/79, 17352/81, 126027/79 and 155835/79 (the term "OPI" as used herein refers to a "published unexamined Japanese patent application") and U.S. Pat. No. 4,131,469, in addition to the above-described U.S. Pat. No. 3,958,995.
The above-described Research Disclosure, Number 15162 also describes water-dispersable latex mordants. However, it contains no mention of the method of adding fading inhibitors upon aqueous coating of mordanting layers containing these water-dispersable latex mordants. As for methods for adding fading inhibitors, when they are water-soluble ones, it is presumed that the method comprises adding directly to an aqueous coating solution because they are easily dissolved in the coating solution. When they are water-insoluble or slightly soluble ones, methods for adding such fading inhibitors to photographic elements include, judging from common sense, known techniques described below such as:
(1) a technique comprising dissolving the above-described fading inhibitor in a substantially water-insoluble high boiling point organic solvent [e.g., alkyl esters of phthalic acid (such as dibutyl phthalate, dioctyl phthalate, etc.), trimellitic acid esters (such as tri-t-octyltrimellitate, etc.), aromatic ethers, phosphoric acid esters (such as diphenyl phosphate, triphenyl phosphate, tricresyl phosphate, dioctylbutyl phosphate, etc.), citric acid esters (such as tributylacetylcitrate, etc.), alkylamides (such as N,N-diethyllaurylamide, etc.) or so on]. The resulting solution was emulsified and dispersed into a hydrophilic organic colloid aqueous solution (as described in, e.g., U.S. Pat. No. 2,322,027 and so on), PA0 (2) a technique of emulsifying and dispersing the fading inhibitor using water-insoluble high boiling point solvents in combination with assistant solvents (e.g., water-soluble solvents such as methanol, acetone, methyl cellosolve, etc., and substantially water-insoluble solvents such as ethyl acetate, butyl acetate, etc.) (which may be referred to U.S. Pat. Nos. 2,739,888 and 3,351,681, Japanese Patent Application (OPI) No. 59943/76 and so on), PA0 (3) a technique of emulsifying and dispersing the compound directly into a hydrophilic organic colloidal solution when the compound itself is oily matter at ordinary temperatures, PA0 (4) a technique comprising dissolving the compound into a water-soluble solvent (e.g., acetone, methyl cellosolve, methanol, ethanol or the like) and then dispersing the resulting solution directly into a hydrophilic organic colloidal coating solution, PA0 (5) a technique comprising dissolving the compound in a water-miscible organic solvent and thereto adding little by little an aqueous loadable latex to obtain a dispersion in which the compound is incorporated into the latex (as described in, e.g., Japanese Patent Application (OPI) No. 59943/76), and several techniques analogous thereto (as described in, e.g., Japanese Patent Application (OPI) Nos. 59942/76, 110247/79, 32552/79, 107941/79 and so on).
According to the above-described techniques (1) to (3), the size of dispersed particles in the dispersions obtained are generally within the range of about 0.1.mu. to about 2.mu.. This causes a lowering of the maximum density due to a light scattering phenomenon, if the photographic element is in a wet state through photographic processings. In addition, since surface active agents used upon dispersion are carried in mordanting layers, a drop in the mordanting power of mordanting agents toward diffusible anionic dyes occurs. Moreover, techniques (1) and (2) are also disadvantageous because they tend to provide thick mordanting layers.
According to technique (4), the dispersion obtained contains large-size dispersed particles. Therefore, the maximum density is lowered and lumps come to the surface of the mordanting layer to spoil its surface properties.
According to the technique (5), the mordanting layer becomes thick. Furthermore, in many cases the surface of a loadable latex has an anionic character. This is because most loadable latexes have, as described in the above-described patent specifications, carboxyl groups, carboxylate groups, sulfo groups, sulfonate groups or sulfate groups, and anionic surface active agents are commonly used upon emulsion polymerization thereof. Therefore, mixing the loadable latex with cationic mordanting agent latexes causes coagulation. Even if surfaces of loadable latex particles are not anionic, a mixture of two or more of latexes is extremely unstable, and tends to produce coagulations.
Accordingly, development of novel methods for adding fading inhibitors to mordanting layers without lowering the maximum density have been desired.
Methods of dispersing hydrophobic compounds through the loading of aqueous latexes with the hydrophobic compounds have been disclosed in, e.g., Japanese Patent Application (OPI) Nos. 59942/76, 59943/76, 32552/79, 107941/79, 110247/79. Such dispersions have become feasible by the use of various techniques. However, the characteristic of these loadable aqueous latexes is that they substantially contain small fractions of monomer units having hydrophilic groups selected preferably from a group consisting of a carboxyl group, a carboxylate group, a sulfo group, a sulfonate group and a sulfate group. Therefore, such loadable latexes have no function except to act as media for dispersing hydrophobic substances effectively. Under these circumstances, the development of loaded polymer latex compositions with more functions imparted by loading polymer latexes and which have not only a dispersing function but also other functions with hydrophobic substances has been desired.